14G PROCEEDINGS OF THE ACADEMY OF 



over 100, and had compelled the workmen, for the time Ijeing, to 

 suspend \york. The earth was found to contain over 75 per cent. 

 of sulphate of protoxide of iron, and the heating had been due to 

 the rapid absorption of ox3'gen by sulphuret of iron, disseminated 

 throughout the earth in a finely divided condition. 



Change of Habit through Fungoid Agency. Mr. Thomas Mee- 

 HAN referred to a former communication in which he exhibited 

 specimens of Euphorbia cordata, or E. humisirata, collected by 

 him in the Rockj^ Mountains, and which, normally procumbent, 

 had assumed an erect habit on being attacked by a fungulus ^ci- 

 dium Euphorbias hypericifolipe. 



He now found that the common trailing Eiqohorbia of our sec- 

 tion, E. maculata, when attacked by the same fungulus, assumed 

 the same erect habit. There was an additional interest in this 

 observation, from the fact that with change of habit of growth 

 there Avas a whole change in specific character in the direction of 

 E. hypericifolia. In a comparison of the leading characters of 

 the two species, we see that in E. maculata there is a profusely 

 hairy stem, while that of E.hyyericifolia is nearly smooth. The 

 same is true of the fruit. The leaves of the former species are 

 ver}' oblique at the base the latter nearly regular. The flowers 

 are produced in all the axils. In the E. hypericifolia the stems 

 have a tendeucj'' to be nodose at the joints, while E. maculata is 

 nearly free from this character, and the floAvers are mainly in 

 heads at the ends of the branches. The E. maculata, after the 

 fungoid attack becoming erect, also becomes nodose, and has the 

 flowers on the ends of the comparatively smooth branchlets, while 

 the leaves have lost their pointed obliquit}^ ; and, in short, all the 

 characters make an intermediate between the two species. 



He said it would not be fair to assume, from these facts, that 

 Eupihorbia hypericifolia was an evolution from E. maculata, but, 

 as there could be no doubt that nutrition was one of the fac- 

 tors in the government of form, we could sa}' that certain phases 

 of nutrition, brought about b}" an attack of a minute fungus, 

 would change the characters to the direction of those in that 

 species. 



September 29. 

 The President, Dr. Ruschenberger, in the chair. 

 Sixteen members present. 



There not being a suflScient number of members present for the 

 transaction of business, in accordance with the B3'-Laws, the 

 meeting adjourned until October 6. 



On favorable report of the Committee to which it was referred, 

 the following paper was ordered to be printed: ' 



